Flue gases from furnace go through cyclone that works as a centrifugal filter, retaining and separating biggest particles. Some of flue gases goes out to stack and some goes down to a loop seal, kinda as bubble bed and finally returns to the furnace.
Thank u for ur reply.And my doubt is how only the unburnt particles return to furnace and how the jseal air is maintainted such that only unburnt particles return from loopseal to furnace?
Not all the unburnt fuel returns to the furnace, the point is that the particles that escape from cyclone have some unburnt fuel too, but as their size is small this quantity is small, so you have some losses in the fly-ash but they are little.
Hi...cyclone is an equipment working on the principle of centrifugal precipitation on losse if inertia of as particles which gets collected in its bottom cone. In the CFBC boiler which is basically one type of atmospheric bubbling bed boiler the bed temperature is maintained by the hot/cold ash recirculation back to the bed vide the ash collected in the cyclones/u beams/ MDCs. In hot cyclone the ash recirculation quantity to fuel fired ratio is around 80 & for cold cyclone cfbc is around 12 to 20 times. Its not necessary that the ash recirculated back is containing full of unburnt carbon. mostly for high efficiency cyclones the ash/ dust particles upto 40microns are collected. so those unburnt carbon particles which got missed in the bed & free board combustion zones gets collected in the cyclones for reburning in the bed. also the ESP/bagfilter ash recirculation helps in reducing the unburnt carbon in flyash also. hope this clarifies your query.
Bijoy B Menon
9689895795
CFBC Boiler 
Re: CFBC Boiler
